By Thu T. A. Nguyen, Publishing Associate: Researcher and Writer at Save the Water | March 08, 2024

The rising amount of toxins found in drinking water sources has made water filtration more and more necessary. Water filtering has been in practice for thousands of years, as early as 4000 B.C. Water treatment has been found in all major civilizations: Mayas, ancient Egypt, Chinese empires, the Romans, and so on. Water filtering methods have advanced over time, and surprisingly, many of them are still used to this day. Therefore, knowing the history of water filters can help us use them well. This article aims to introduce you to the most basic ideas behind water filtration.

What can be in the Water?

In the early days, cloudiness (or turbidity) was the main reason for water filtration. But as science progressed, we’ve found bacteria, sediments (sand, clay, and other soil particles), chemicals, and toxins in water. In rare cases, small radioactive particles have also been detected in water.  

Water Filtration Methods in Ancient Times

Ancient Sanskrit and Greeks used charcoal, sunlight, boiling, and straining as methods for cleaning water.

From around 1500 B.C., aluminum sulfate, called alum, has been added to water to make it clearer. Alum forces dirt out of water, and lake managers still use it to improve water quality today.

Greek and Roman engineers used zeolites 2700 years ago to build large water-related structures, such as bridges, dams, and harbors. Furthermore, the ancient Mayans used quartz and zeolite to make complex water-cleaning systems between 2500 to 1100 years ago.

They used quartz as a sieve and zeolite (a mineral from volcanoes) as a sponge to hold and separate particles from water. These natural crystal materials can remove microbes, metals, and toxins from drinking water.

Water Filtration Methods in Modern Times

In the 1800s, people in Europe used sand filters. During this period, scientists also started to better understand contaminants that couldn’t be seen by the naked eye. 

This base knowledge became a major driving force for more effective water treatment in the U.S. in the 1900s. In addition to filtering and reducing turbidity, chlorine was used for the first time in 1908 in New Jersey. Moreover, ozone’s antimicrobial properties were discovered in Europe around this time and became widely used in the 1970s and 1980s.

Starting in the 1960s, it was agreed upon that man-made chemicals were also a problem found in drinking water. At this time, using charcoal for odor and organic chemical removal became more common. 

In many cultures, people have tentatively used charcoal to treat water as early as 400 B.C. Activated charcoal (or activated carbon) is a form of charcoal that undergoes further processes to filter out more toxins. This material is often seen in many applications:

• Gas masks 
• Medicine
• Agriculture
• Water purification, like powdered activated charcoal (PAC) and granular activated charcoal (GAC) 

Advancements in Membrane Filtration

Besides the use of various natural materials for filtration, man-made materials have been used in water purification since the 1980s. After 30 years of development, porous membranes have become an economical way to treat drinking water. There are a variety of membranes serving different purposes.

The first class of membranes, called pressure-driven filters, differs by pore (hole) sizes. They remove stuff from the water based on how big they are. Their pore sizes range from 0.1 to 0.001 µm. Microfiltration membranes, with the largest pore size of 0.1 µm, won’t let sediment, algae, and bacteria through. Ultrafiltration membranes, with a pore size of 0.01 µm, will remove small colloids and viruses. Nanofiltration membranes will only allow anything smaller than 0.001 µm through, removing things like larger divalent ions of certain salts.

Another type of man-made filter is reverse osmosis (RO), also a pressure-driven process, that was first tested in the 1960s. Since then, several materials have been used to produce membranes for RO.

To understand how the RO process works, we first have to understand osmosis. Osmosis happens when a penetrable divider separates two liquids with different contents. Naturally, water moves from the side with a lower concentration to the side with a higher concentration.

RO uses force (or pressure) to push the water to do the opposite. In addition, the RO membranes are made to hold salts and other matter with low molecular weight. As a result, low-salt water can be achieved at the end of this process. 

Other types of filters, such as electrodialysis (ED), electrodialysis reversal (EDR), and forward osmosis (FO) membranes are also commonly used in desalination processes. These methods use other scientific approaches but aim to achieve the same goals. More information about these membranes can be found here.

Takeaway

We may feel overwhelmed by new contaminants that threaten our drinking water in recent times. They include per- and polyfluorinated substances (PFAS) and microplastics, radioactive materials, antibiotics, heavy metals, and so on. However, we should not forget the constant development of water-cleaning technologies to improve our health needs. 

This article focuses only on the basic development of filters. However, other technologies can be used together with water filtration:

• Ultraviolet (UV) water disinfection system
• Ion exchange process
• Biological treatment 
• Natural absorbents (e.g. fruit peel waste) 
• Solar wastewater treatment 
• Ecofriendly magnetic nanoparticles

By Lauren Hansen, Staff Researcher/Writer at Save the Water | June 27, 2022

Keeping the correct level of ammonia in water is a tricky balance to strike. Though it disinfects our water, too much of it is bad. Engineers at a plastics engineering systems company have developed a new technology that removes enough ammonia from water without removing too much. However, any technological advance in ammonia filtration is moot without uniform ammonia regulation in the US water supply.

What is ammonia and what is it used for?

Ammonia is a naturally-occurring chemical that comes from decomposed animal and plant matter. It has a variety of uses in everyday life:

• Soil fertilizer to encourage plant growth
• Effective surface cleaner
• Water disinfectant

Ammonia is used in small concentrations to disinfect drinking water. However, too much ammonia in water is harmful to humans and wildlife. 

How is ammonia harmful?

Water with high concentrations of ammonia harms, even kills off, aquatic life and produces harmful algal blooms. In humans, consuming high amounts of ammonium  causes “… corrosive damage to the mouth, throat, and stomach.”

When ammonia concentrations are too high, it’s difficult to remove from water because it is highly soluble. High solubility means that ammonium easily dissolves in water. High soluble materials are therefore more difficult to filter out. 

New filtration technology for biomass and ammonia

Companies and organizations, such as the EPA, have sought over the decades ways to remove excess ammonia from water. 

One of the latest developments in ammonia removal comes from Brentwood, an engineering firm. Brentwood has developed a new, scalable technology called AccuFas to remove 85-90% of ammonia from water. 

Brentwood’s AccuFas solution uses a fixed-growth surface, meaning it stays in place and does not move with the water stream. The fixed growth surface acts as a filter for biomass. As a reminder, biological matter, such as urine and feces, is a source of ammonia. The AccuFas filter pushes just the right amount of air through the water in order to get “… optimum  contact between the waste stream and  biomass.”

AccuFas was introduced as a pilot technology in an undisclosed mid-sized suburb looking to reduce its ammonia levels. It addressed a difficult challenge of, on the one hand, keeping ammonia levels low enough but not too low that it fails to disinfect the water supply. AccuFas removed enough ammonia to avoid disinfectant byproducts (DBPs) that it produces while also continuing to disinfect water.

How does ammonia enter the water supply?

Ammonia enters a water source due to naturally occurring or human processes. It comes from naturally occurring sources:

• Decomposed plants and animals
• Animal waste
• Forest fires

It also shows up in the water supply from human actions and processes:

• Agricultural run-off
• Water treatment plants
• Sewage leaks

In the US, there is no standard way to keep human-related ammonia contributions in check.

Ammonia in water: lack of regulation

The regulation of ammonia levels in the US water supply is limited and inconsistent at best. 

Federal regulations are in place in the US to monitor point source dischargers of water pollutants that may include ammonia. Point source dischargers are obvious sources of pollution that are traced to specific places, such as factory wastewater pipes. Ammonia contamination from those sources is, therefore, easier to find and reduce. 

However, these regulations do not and cannot cover non-point source dischargers, which are more ambiguous sources of ammonia. Runoff is an example of a non-point source discharger because it is unclear where it came from. Possible sources include farmland, construction, lawns, and others. 

Because it’s not clear where exactly the ammonia comes from in some instances, it makes it difficult, if not impossible, to regulate non-point source discharges. For that reason, ammonia can still enter the water supply. 

The EPA provides a general aspiration to follow. Its most recent guidance from 2013 recommends no more than “17 mg Total Ammonia Nitrogen (TAN) per liter at pH 7 and 20°C for a one-hour average duration, …” Ammonia levels cannot exceed this amount more than once on average during a three-year period. 

As an additional measure in the 2013 report, the EPA limits ammonium to “1.9 mg TAN/L at pH 7 and 20°C for a 30-day average duration.” As with the previous measure, ammonia levels may not go above 1.9 mg TAN/L more than once on average over the course of three years.

However, these are merely recommendations from the EPA; there are no strict regulations, let alone enforcement of ammonia levels in the US. The EPA defers to individual states in regulating ammonia in water sources:

“EPA’s recommended water quality criteria are not rules, nor do they automatically become part of a state’s water quality standards. States must adopt into their standards water quality criteria that protect the designated uses of the water bodies within their area.”

Ammonia in small amounts indeed plays an important role. It disinfects the water we drink. However, the loose regulatory framework for controlling its concentrations makes it just an option for local and state-level environmental agencies to adopt. This opt-in model depends on individual states. It thus prevents consistently-balanced levels of ammonia in drinking water across the country. 

While some states may regulate ammonia levels in water, others may not. Without a common regulatory landscape, states’ lack of action counteracts any benefits from states that do take action to keep ammonia concentrations at safe levels in the water supply.